An air deflector is usually used in connection with a windscreen wiper, generally consisting of a windscreen wiper arm carrying in an articulated manner a windscreen wiper device comprising a mounting which carries a windscreen wiper blade adapted to wipe a glass surface, such as the windscreen of an automobile vehicle.
The general purpose of the air deflector is to deflect the air streams impinging on the wiper device when the vehicle is moving at high speed, in order to prevent lifting of the wiper device, and in particular of the windscreen wiper blade, as a result of the aerodynamic forces created by the air stream, which would leave an intact film of water on the glass surface, eventually interfering with the driver's vision.
A known deflector, in particular that described in FR-A-2 621 288, comprises a shaped part comprising a substantially flat first region extending rearwards from a front edge, the said first region being slightly inclined relative to the mid-plane of the surface to be wiped and a second region following the first and having a greater inclination than the inclination of the first region, the said shaped part being situated at a sufficiently small distance from the surface to be wiped to create a surface effect producing a relatively large decrease in pressure below the deflector, that is to say in the region between the surface to be wiped and the shaped part, which allows correct application of the blade against the glass surface.
This type of deflector is mounted in front of the windscreen wiper device with respect to the direction of flow of the air streams which flow over it.
It has been shown that the air streams, after flowing along the shaped part, impinge against an obstacle formed in part by the wiper blade. This obstacle represents a significant disadvantage since it creates turbulence in the circulation of the air streams which can alter the desired pressure reduction below the shaped part of the deflector and consequently impair the desired surface effect.